Stairways employed in buildings and other structures present difficulties to non-ambulatory individuals. For example, a non-ambulatory individual confined to a personal vehicle such as a wheelchair cannot easily negotiate common stairwells. To accommodate such individuals, separate elevator lifts, moving chair arrangements, or ramps are often provided. In stair structures extending a vertical distance that is less than a building story, such as those typically used near the entrance to a building, a separate elevator lift is not always practical, particularly in outdoor environments. In such cases, separate ramps or moving chair arrangements may be provided which facilitate vertical travel by a personal vehicle.
One drawback to the use of a separate ramp to provide personal vehicle access to elevated surfaces is that suitable ramps consume relatively large amounts of space. As a result, existing buildings must often be substantially altered to accommodate the installation of a ramp. In many circumstances, space constraints within or surrounding the building make installation of a ramp impossible.
Moving chair arrangements offer a solution in such low rise environments. Moving chair arrangements comprise a chair that slides diagonally up and down the stairway. Such arrangements require that the personal vehicle be separately transported up or down the stairway. Because personal vehicles can be quite heavy, separate transport of the personal vehicle can be difficult. Moreover, the movable chair itself, when not in use, still occupies stairway space and thus dictates the appearance of the staircase.
Separate vertical wheelchair lifts have also been employed for such low rise environments for use in situations in which there is inadequate room for an access ramp. Such devices, however, while consuming less space than a ramp, nevertheless consume valuable access space and dictate certain architectural parameters. Moreover, separate wheelchair lifts may be impossible to implement in hallways or other narrow environments.
In an attempt to address some of the concerns of the separate vertical lift, lifts have been developed that cooperate with a staircase to provide a vertical lift that fits within a hallway or narrow environment. For example, U.S. Pat. No. 4,457,402 to Del Vecchio et al. shows a lift that is disposed directly in front of a low rise staircase that extends from a lower surface to an upper surface. The lift provides vertical transport of wheelchairs from the lower surface to the level of the upper surface. When the lift rises, the stairs collapse upward to form a bridge platform that allows travel from the lift platform over the area normally occupied by the staircase to the destination upper surface.
Another proposed design of a lift that may be located in a narrow environment is found in U.S. Pat. No. 5,234,078 to Smith. In the Smith patent, a lift platform is located on the upper surface directly behind the ascending stairs. In other words, the lift platform forms a portion of the upper surface. The lift platform provides transport between the upper surface and the lower surface through vertical movement. When the lift platform lowers to the level of the lower surface, the stairs collapse so that they too are substantially on the level of the lower surface. When the lift platforms rises to the level of the upper surface, the stairs reconfigure into a staircase.
A drawback of the designs found in the Del Vecchio et al. and Smith patents discussed above is that they require space equivalent to the area of the lift platform either completely in front of or completely behind the staircase. In some cases, such area is not available. Moreover, because the lift platform is located completely outside the footprint of the staircase, the lift platform creates a potentially displeasing architectural discontinuity with the surface at which it normally rests while not in operation. For example, as shown in FIG. 1 of the Smith patent, the lift structure requires special wall and floor structures that create visible discontinuities along the floor and wall. Likewise, the lift shown in the Del Vecchio et al. patent, undesirable creates a plainly visible discontinuity along the intersection of the platform and lower (ground) surface. Such discontinuities significantly affect the appearance of an architectural structure.
These issues were addressed by Storm in U.S. Pat. No. 5,937,971, in which a rotating rail system is used to create, in one configuration, a flat platform, which can be moved up or down, and in a second configuration, an angled stairway. While this design provided a convertible lift mechanism that could be fitted within a smaller space than the Del Vecchio or Smith patents, it's rail system provides poor support for the platform, and requires a complex system for movement of the rails and/or platform, and is not readily convertible for providing staircases of different heights. As such, each must be custom design for a particular location, or the building must be architecturally modified to meet the design parameters of a standard staircase. Further, there is no apparent mechanism for adjustment of the stair height to comply with various local building regulations, or the like.
As such, there continues to exists a need, therefore, for a improved lift structure which is convertible from stairs to a moving platform, in order to provide access between a lower surface and an upper surface. The design must continue to provide a convertible lift assembly that has reduced impact on the architectural and/or design aspects of a structure, and which may be employed in structures with space constraints.